Motor control and braking system



March 28, 1944. G. R. PURIFOY 2,345,150

MOTOR- CONTROL AND BRAKING SYSTEM Filed Aug. 11, 1942 2' Sheets-Sheet 1NNN NN March 28, 1944. G. R. PURIF'OY MOTOR CONTROL AND BRAKING SYSTEM 2lSheets-Sheet 2 Filed Aug. 11, 1942 TTORNEY Patented Mar. 28, 1944 MOTORCONTROL ANDl BRAKING SYSTEM George R. Purifoy, Pittsburgh, Pa., assgnorIso` Westinghouse Electric & Manufacturing Company, East Pittsburgh;Pa., a corporation of Pennsylvania,

Application August 11, 1942, Serial No. 454,358

7 Claims.

My invention relates, generally, to control ysys-l tems and, moreparticularly, to systems for controlling the acceleration and thedeceleration of the propellin-g motors cf electric vehicles;

vAn object of my invention, generally stated, is

to provide a control system for electrically-propelled vehicles whichshall be simple and eflicient in operation and which may be economicallymanufactured. and installed.

A more specific object of my invention is to coordinate theelectricalfbrake andthe .air-brake syst-ems of an electrically-propelledvehicle.v

Another object of my` invention is'to increase the smoothness ofoperation of an electricallypropelled vehicle, particularly during. the`decelerating period.

A further object of my invention is to provide a control system suitablefor application on 'a single car or on a plurality of cars' connectedtogether for multiple-unit operation. Y i

Other objects of my invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of myinvention, both the accelerationand the dynamic braking of an electrically-propelled vehicle areprimarily controlled by a motor driven accelerator of the type describedin Patent No. 1,991,229, issued February 12, 1935, to L. G. Riley. Invthe present system the dynamic and the air-brake systems are socoordinated that a practically constant rate of deceleration ismaintained during the application of the brakes.

For a fuller understanding of the nature and objexztsA of myinvention,reference may be had to the following detailed description, takenV inconjunction with the accompanying` drawings, in which:

Figure 1 is a diagrammatic viewof a control system embodying myinvention;

' Fig. 2Yis a chart showing the sequence of operation of a portion ofthe apparatus illustrated in Fig. l; and

Fig. 3 is a graph showing the performance of a vehicle controlled by thecontrol system illustrated in Fig. 1.

Referring to the drawings, motors Ill and II may be utilized forpropelling a vehicle (not shown). The motor I is provided with anarmature winding I2 and a series-field Winding I3.

Likewise, the motor I'I is provided with an arma I' ture winding I 4 anda series-field winding l5, A line switch LSI is provided for connectingthe motors I0 andV I`I to a trolley I6 Awhich engages-a power conductorI'I that/may be v.energized from any suitable sourceof power such asa'generatng,

station (not shown).k The motors Illand Il are connectedinparallelcircuit relation during acceleration of the vehlcle.A VThey may'also-bev connected fordynamic braking with the. field'winding I5 .of-motorll connected across the-armature I2 of motorV I t and'` the veldwinding I3 ofmotor I0 connected across the armature I4 of motor II,thereby permitting the current in the armature-windings to reverse andcause the motors to act as' generators and decelerate vthe vehicle. Apair of switches BI and B2. is providedforestablishing` theidynamicbraking connections.

Both the acceleration andthe decelerationv of the motorsY I0 and II areprimarily controlled' by a motor driven accelerator4 A which is of thevsame general type as the one described inthe aforementioned Patent No.1,991,229. .The accelerator A 'comprises a circular lbus I8 inside'oflwhich is disposed a plurality of contact lingers 2| to 4U, inclusive,which are progressively forcedl against the bus I8 by a pair'ofrevolving rollers I'SlandZll.` y'

The rollers I9 and 20 are driven byfapilot motor PM through'a-shaftftl'.. AThe pilot motor PM is provided'wit'h an armatureWinding. 44 and two -fieldwindings and 46,1one foreach'direc;

tion of rotation of' the motor. TheH energy 'for-'- operating' thepilot' Ino'tol and' the Control apparatus may be 'supplied by a batteryorzo'th'er suit#v able source of control energy.

A limit relay LRis provided for controlling the operation of the pilotimotorPM during both acceleration and' deceleration oflthe 'Vehicle A'Asshown, the relay LR is-provided with several differentA actuating coils'which functionl to operate" the relay duringcoastingof the vehicle as'well as during accelerationv and dynamic braking.

Thus', a series coil '41 is connectedxinthe 'motorf ci'rcuit. duringboth' acceleration and deceleration of the Vehicle. A spotting coilf49:is-connected across aresistor 5I to -be energized'infaccordance withthe motor current during'coasting of the "i vehicle,thereby providing ameans of spotting the accelerator A. A variable rate coil .48 -isenergized durin'gacceleration ofthe vehicle andan additional rate coil52is energized during coast.-

ingandf dynamic braking for controlling the' ac.-A

The relay LR'fis celerating .and braking rates. alsoprovided withatickl'ercoil 53 which functionstoicause a vibratory action ofthe`relay'in` a manneriwell known inthe art. f

In orde'r to provide for'changing these'ttii'igofv the relay LR, therebygoverningthe rate ciacdesignated BC, which is utilized during dynamicbraking of the vehicle. Since the controller is operated by the operatorof the vehicle, the accelerating and braking rates may be varied by theoperator as desired. y

The accelerator A is provided with resistors 58 and 59 for controllingthe current in the motors I and H. The resistor58 is divided'into anumber of subdivisions which are connected to Y the contact fingers 2|to 30, inclusive, and the resistor 59 is divided into subdivisions whichare connected to the contact fingers 3| to 40, .inclusive. In .thepresent system, the'resistors 58 and 58 are connected in -the motorcircuit in series-circuit relation --during lboth, acceleration anddynamic braking, thereby making it unnec-v essary to change the resistorconnections when transferring from motoringto` braking operation. Asdescribed in Patent No. 2,254,911, issued September 2, 1941,.to L. G.Riley, the resistor 5|- and an additional resistor 6| are connected inthe motor circuit in parallel-circuit relation to the resistors 58 and59 during the motoring operation. Since part of the motor current isdiverted4 through the resistors 5l and 6|, the heating effect on theaccelerator is reduced and also arcing of the contact fingers on theaccelerator is reduced. i

As shown, the accelerator A is provided with a drum switch 62 having aplurality of contact segments 63 to 61, inclusive, and cooperatingycontact iingers which engage the contact seg ments as the yacceleratoris driven by the shaft 4|. The reference numerals 2|' to 30 indicate thecontact iingers over which the roller I9 travels while the contactsegments are engaged by their-respective contact lingers. It will beseen that the roller 2li-travels over ilngers 3| to 40 while the'rollerI9 travels over ngers 2| to 30. I'he function of the different segmentsof the drum switch 62 will ybe ;explained more fully hereinafter.

In addition to the accelerator andthe control switches previouslymentioned, numerous' other switches are provided and perform certainswitching operations. These include a switch LSZ for shunting a resistor8&8 from the motor circuit, a switch MI for connecting themotors to theaccelerator during acceleration of "the vehicle, a switch G forAconnecting the'accelerator` resistors to ground during acceleration,'aswitch. M2 for connecting the motors directlygto ground.

through the switch G after the acceleratorresistors have been shuntedfrom Vthe motor circuit by the accelerator rollers, a switch R forconnecting the resistors 5| and 6| in the motor circuit duringacceleratiompas previously .described, and aeld shunting switch S havingcontact members Sl 'and'SZffor shunting th iield windings I3and"|5,'re`spectively.

In order to permit the present system to. be utilized oncars which are'operated in multiple unit trains and controlled fromv one controlstation at the headof` the train, a' braking relay BR is provided. The`relay BR permits dynamic braking to be established simultaneously on allthe cars of the train. 'Ihe energization of the relay BR is controlledby the braking controller BC which may also be utilized to control theair brake system (not shown). Thus, when the braking controller at thehead of the train is operated, all ofthe relays BR throughout the trainare energized to permit dynamic braking to be established on all themotors of the train. The controllers AC and BC are electricallyintcrlocked to prevent improper operation of the equipment.

As fully described and claimed in my copending application, 'Serial No.442,764, filed May 13, 1942, now Patent No. 2,318,332, interlocks areprovided on the switch R for so controlling the operation of the pilotmotor PM that the acceleratormay be stopped and held on any positionbyVA operating the switch R which is controlled by the acceleratingcontroller AC. Thus, the controller AC is provided with a switchingposition-and the Variable rate positions.

When the controller is actuated to the switching position, the switchesLSI, MI and G are closed to connect the motors to the power circuit inseries-circuit relation with the resistors 58 and 59 of the acceleratorA and also in series-circuit relation with the resistor 68. At thistime, the accelerator A will remain in 'its initial position. After thecar has started moving and the rate of acceleration is to be increased,it is only necessary to actuate the controller to one of the ratepositions, thereby closing the switch R to connect the resistors 5| and6| in parallel-circuit relation to the motors and also closing theswitch LS2 to shunt the resistor 68 from the motor circuit. 'I'heclosing. of the switch R causes the accelerator to rotate, as the pilotmotor is energized through interlocks provided on the switch R, as willbe'described more fully hereinafter.

If it is desired to stop and hold the accelerator on any given position,the controller AC is returned to the switching position, thereby openingthe switch R to deenergize the pilotmotor, and stopping the acceleratorat the desired position. The' opening of the switch R also slightlyincreases the total resistance in the motor circuit toprovideacushioning effect on the motors,v

thereby 'providing a smoother` operation of the vehicle.

Thus, by opening and closing the switch R, the accelerator is caused toprogress or to hold. If automatic acceleration is desired, it is onlynecessary to actuate the controller to any desired rate position and theprogression of the pilot motor will .be under the control of the limitrelay LR. The foregoing feature is particularly desirable-When operatinga vehicle through congested `traffic areas which require that theacceleration of the vehicle be interrupted frequently. Furthermore, theslight increase in the resistance in the motor circuit caused by theopening -of theV switch R andthe switch LSZ, in the foregoing manner,prevents jerking or jumping of the cars during acceleration, as theprogressionof the accelerator is stopped at a desired running speed.

In order to coordinate the air brakes and the dynamic brake,acompensating magnet CM is provided for governing the application of theair brakes in accordance with the dynamic braking current,`thereby.maintaining a predetermined braking or fdecelerating rate ofthe vehicle. As shown, the compensating magnet CM is anelecuonoeualatlodenoe bovinos Pressure regulatiosm ...l-ve 6B and a pairof solenoid colis 59 and mior actuaiins'the valve ,6.0. The .Coil 69 .iseuergized Afrom a battery, or other source ofi constant potential,through the controller BC and is provided for the purpose of overcomingfriction inthe solenoidand valve mechanisms. Y'lhe ,coil 'lll isconnected across the resistor 5| through anA hielo. it. has been 'foundthat when the dynamic brake fades out, there is a drop of approximatelyone mile per hour per second in deceleration at the fadeout of thedynamic brake. r This drop in deceleration iscaused by the slownessofoperation of the compensating magnet to. permit air to be admitted tobrake cylinder.

' I n order to prevent the undesirable drop in deceleration, thecompensating magnet may be either deenergized or the ampere turnsreduced bythe operation of the switch M2 to permit air pressure to buildup in the 'brake cylinders. As explained hereinbefo-re, the switch M2 isoperated to shunt the accelerator resistors from the motorv circuit whenthe accelerator completes the braking cycle'.l Since the'ope'ration ofthe switch M2 is controlled by thev accelerator and the ao'.-celer'ator'is advanced under the control of the limit relay IB, duringdynamicbraking to maintain a predetermined brak-ing currentjthe switchM2 may be util'iaed` to deenergize the compensating magnet suicientlyprior to the fadeout o the dynamic?brake to permit the air to buildup inthe brake cylinders to secure the results depicted by the curve showndotted in Fig.' 3. In this manner a` smoothbrak'ing effect is obtained.In order that the functioning of Vthe foregoing apparatus may be moreclearly understood, the operation of the system will now be described inmore detail. As explained hereinloefore, power may be applied to themotors I9 and by actuating the controller AC to the switching position,thereby closing the switches LSE, Ml, and C- to connect the motors tothe power source. The energizing circuit for theactuating coil 'of theswitch L-,Sl may be traced from positive through a contact segment 1| ofthe controller:

BC,Y conductor 12, a Contact segment 13 of the controller AC. conductor14, an interlock 15 on the switch Bl, conductor 1t, the actuating coilof the switch LSi, conductor 1l, and the contact segment Si! of the drumswitch 62,'to ground. Following the closing of the switch LSi, aholdingcircuit for the coil of the switch is established through aninterlock 18 on the switch LS1. The energizing circuit for the-actuatingcoil of the switch M! extends `from the conductor l5 through t eactuating coil of the switch Ml to ground and the energizing circuit forthe coil of the switch G also extendsv from the conductor 1E tlirouglrithe coilof the switch G to iground.

The closing of the switch LSI, Ml, and G connects the motors tothe-power source through a Conductor 8.4.. the switch LSI. the'.resistor 6 3,

magneto? 332;. the armsturewmdoa i? 'and the ser. seriele winding I totthe meter "it 'GQ tol? 83, the switch MI, conductor 8d, the resistor 59of the accelerator vA, theA bus I8, the resistor 58, conductordand theswitch G to the ground. The ,circuit through the motor extends from theconductor 82 through the series-field wind-- ing i5, conductor B, theseries coil 4'!- or the limit relay conductor 31, .the armature wind--ing I4, conductor 83, the switch MI, andthence through the accelerator Aand the switch G to ground through a circuit previously traced.

As explained h ereinbeforathe motors Iii and Iloperate at a relativelyslow speed since all o f the accelerator' resistance remains connectedin the motor circuit. Ifl it is desired to increase the speed of themotors, the controller AC is actuated to one of the rate positions,depending upon 'the rate of acceleration desired. When the controller ACis actuated to one of the rate positions, the switch R is closed toconnect the` resistors 5| and El in vparallel-circuit relation to theresistors of the accelerator A, thereby reducing the duty imposed uponthe accelerator and also making it possible to connect the resistors 58and 59 of the accelerator invseriescircuit relation during motoring aswell as during dynamic braking. The energizing circuit for the actuatingcoil of the switch R may be traced from a contact segment 88 lof thecontroller AC through conductor 89, an interlock 9| onthe switch LSI,conductor 92, and the actuating coil of the switch R torground.

Following the closing of t f e switch R, the

i switch LS2 is closedjto shuntthefresistor 58 from the motorcircuit.The energizing circuit for the actuating coil of the switch L52 extendsfrom the conductor "J5 through Yar1,int erlocl, 13l on the switch R,conductor S, and the actuating coil of the switch LS2-to ground. e y

. As explained hereinbefore, the closing of the switch R alsoestablishesy a circuit for energizing the pilot motor PM to advance theaccelerator A, the pilot motor beingunder the control oi the limit relayLR, which, as explained hereinbefore, is responsive to the motorcurrent. The energizing circuit. for the-pilot motor may be traced frompositive through a resistor 95, a conductor. 95, the ticklercoil 53,contact members 97 98 ofV the relay LR, conductor l99, an interlock ||l|of the switch G, conductor |02, an interlock |93-on thel switch R,conductor HM,v any interlock llon'the switch M2, conductor |66, thecontactv segment- 66, of the drum switch 92, conductor winding 4d ofthemotor` PM -to ground.

t As explained hereinbefore, the motor PM advances the accelerator Aunder thecontrol of the limit relay-LR unless the controller AC isreturned to the switching position to deenergize the actuating coils/ofthe switches Rand LSB, thereby causing these switches -to open. Theopening of the switch l?, opens the interlock lill? carried byV thisswitch, thereby deenergizing the pilot motor PM independently of anyaction of the limit relay LR. Accordingly, the pilot motor PM is stoppedand `,the accelerator A` will remain in .the position in whichv itwas'at the time of theopening of the switch R Vuntil the controllerv isactuated to a. rate position to yreclose the switchR, atwhich time theaccelerator will continuato advanceunde-r the control ofthe limitrelay-m .lhuowening'of the switohfR. Qplls the. parallel circuit throughthe resistors 5| and 6|, thereby slightly increasing the totalresistance in the motor circuit. Likewise, the opening of the switch LS2increases the resistance 4in the motor circuit by reinserting theresistor 68 in series with the motors I and II. When these switches arereclosed, the resistors I, 6| and 68 are reconnected in the motorcircuit in the manner hereinbefore explained. In this manner, thevehicle may be held at any desired speed when operating through traiiicand a smoother operation of the vehicle is obtained by the cushioningaction of the foregoing resistors in the motor circuit.

When the accelerator Al nears the end of its travel in a forwarddirection, the switch M2 is closed to connect the motors l0 and I Idirectly to the ground. The energizing circuit for the actuating coil ofthe switch M2 may be traced from the previously energized conductor 92through an interlock |08 on theswitch LS2, conductor |89, the actuatingcoi1 of the switch M2, conductor |I and the contact segment 63 of thedrum switch 62 to ground. A holding circuit for the coil of the switchM2 is established through an interlock |I2 carried by the switch.

The closing of the switch M2 connects the motors I9 and I directly 'toground through the switch G, thereby permitting the accelerator A to bereturned to its initial position in preparation for an establishment ofthe dynamic braking circuit vfor the motors. The closing of the switchM2 also opens its interlock'l thereby interrupting the energizingcircuit for the pilot motor PM, which operated the motor in the forwarddirection. Furthermore, the closing of the switch M2 energized the-olield Winding 46 of the pilot motor, thereby causing it to operatev in thereverse direction to return the accelerator A to its initial position.At this time, the energizing circuit for the pilot motor may be tracedfrom positive through the resistor 95, conductor 96, an interlock l I3on the switch M2, conductor II4, the contact segments 61 of the drumswitch 62, conductor H5, the oil field winding 46 and the armaturewinding 44 of the motor PM to gr'ound.

If it is desired to permit'the vehicle to coast, the motors I0 and IImay be disconnected from the power source by actuating the controller ACto the oil position, thereby deenergizing the actuating coils for theswitches LSI, LS2, Ml, M2, R, and G. When the controller AC is returnedto the off position, the switches BI, B2

and S are closed to establish a dynamic braking circuit for the motorsprovided the accelerator A has returned to its initial position toinsert the full amount of its resistance in the motor circuit.

yIn this manner, a small amount of current is permitted to circulatethrough the motors during coasting of the vehicle, as described inPatent 2,078,684, issued April 27, 1937, to L. G. Riley. However, thecirculating current isof such a low value that it does not materiallyaffect the coasting characteristics of the vehicle. The energizingcircuit for the actuating coil of the switch BI may be traced frompositive through a contact segment I IS of the controller AC, conductor|I1, an interlock I I8 on the switch LSI, conductor I |9, the actuatingcoi1 of the switch B I, conductor |2I and the contact segment 65 of thedrum switch 62 to ground. The energizing circuit for the actuating coilof the switch B2 extends from the conductor I I9, through the actuatingcoil of the switch B2, conductor I2I, and the segment to ground. Aholding circuit for the switches BI and B2 is established through aninterlock |22 carried by the switch BI. The energizing circuit for theswitch S extends from the conductor I I9 through an interlock |23 on theswitch B2, contact members |24 of the relay BR, conductor |25 and theactuating coil of the switch S to ground.

As explained hereinbefore, the closing of the switch S shunts the eldwindings I3 and I5 of the motors I9 and II, respectively, through eld.

resistor 5I which is in the motor circuit at this time. The energizingcircuit for the spotting coi1 may be traced from one terminal of theresistor 5| through conductor |28, an interlock |29 on the switch G,conductor |3|, contact members |32 of the relay BR, conductor |33, thespotting coil 49 and conductors |34 and 84 to the other terminal of theresistor 5|.

Since the current generated by the machines I0 and I during coasting isproportional tothe speed of the vehicle, this current may be utilizedfor spotting the accelerator A, that is, matching the position of theaccelerator with the speed of the vehicle, thereby insuring that theaccelerator will be in the proper position for the utilization ofdynamic braking to decelerate the car. As previously explained,. theaccelerator is under the control of the limit relay LR during coasting.The contact members of the limit relay are so connected in the circuitfor the pilot motor that the motor may be operated in either directionde-l pending upon the speed of the car.

Thus, with the contact members 91 and 98A closed, the pilot motoradvances the accelerator to decrease the resistance in the motor circuituntil the point is reached at which the motor current is suilicient tooperate the relay LR to open the contacts 91 and 98. Should the cardecrease in speed, which would result in lower 50, mo-tor current, thecontact members 91 and 98 are closed to further advance the accelerator;

However, should the car increase in speed during coasting, resulting ina suilicient increase in the motor current to cause the contact member91 to engage a contact member |35 of the relay LR, the pilot motor willbe operated in the reverse direction to return the accelerator towardsits initial position, thereby increasing the resistance in the motorcircuit and matching the position of ther accelerator with the speed ofthe car. The circuit for forward operation of the pilot motor may betraced from positive through the resistor 95, conductor 9S, tickler 91and 98, conductor 99, switch Bl, conductor |02, an interlock |31 on theswitch MI, conductor I 94, the interlock |95 on the switch M2, conductorIUS, the segment 66 on the drum switch 62, conductor |01, the on fieldwinding 45 and the armature winding 44 to ground. The circuit forreverse operation ex,- tends from the contact member |35 of the relay LRthrough conductor |I4, the segment B1 of the drum B2, conductor I I5,the 01T eld winding 45 and the armature winding 44 to ground.

As described and claimed in my copending apcoil 53, contact members aninterlock |36 on theA plication, Serial. No. 442,763, filed May 13,1942, now Patent No. 2,318,331, the switch M2 is utilized to permitadvancement of the accelerator during coasting and braking, but preventsits advancement while the vehicle is standing still. "When theaccelerator nears the end of its travel in a forward direction duringeither coasting or braking, the switch M2 is closed and, as explainedhereinbefore, the operation of the switch M2 opens its interlock |55 tointerrupt the energizing circuit for the on field of the pilot motor andcloses its interlock ||3 to establish an energizing circuit for the oneld of the pilot motor, thereby returning the accelerator to its initialposition. During coasting or braking, the energizing circuit for theactuating coil of the switch M2 is established from the previouslyenergized conductor H9 through an interlock |41 on the switch B2andconductor |09 to the actuating coil of the switch M2 and thencethrough the contact segment 63 of the drum switch 62 to ground, asdescribed hereinbefore.

Thus, the switch M2 is closed when the accelerator nears the end of itstravel in a forward direction. If, for instance, the car has coasted toa stop after a light brake application, the accelerator roller willprogress through Vthe operation of the limit relay to cause the switchM2 to close in the manner hereinbefore described. The closing of theswitch M2 causes the'accelerator to` be returned to the initial positionand be held there for a reapplication of power. The same action takesplace onrall the cars of a multiple-unit train, thereby insuring thatallaccelerators are in the initial position for a reapplication ofpower'.

In the event that both the controller AC and the controller BC areactuated to the ofi position, at any time during the operation of thevehicle, the pilot motor PM is operated in the reverse direction toreturn the accelerator toits .initial position through interlocksprovided on the switches LS| and Bl. The energizing circuit for thepilot motor may be traced from conductor 95, through an interlock U32 onthe switch LSL conductor |633, an interlock H on the switch BI,conductor h3, and thence to the off eld winding of the pilot motorthrough a circuit previously traced.

In the event that dynamic braking is required to decelerate the vehicle,the controller BC is actuated to one o1 the braking positions, therebyenergizing the relay BR to change the calibration of the rate coil 52and the spotting coil 49. In this manner, the limit relay LR. isrecalbrated for proper operation during dynamic braking. The rate coil48 is normally energized through either the resistor 54 or the resistor55, depending upon whether the vehicle is accelerating or braking andthe rate coil 52 is energized through a resistor |45. The energizingcircuit for the rate coil 52 extends from either the conductor 89 or theconductor I1 through either interlock |55 or |55 on the switch R. andconductor |56 to the resistor |45 and thence through the coil 52 toground.

As explained hereinbefore, the contact members |32 of the relay BR,shunt a resistor |46 from the energizing circuit for the spotting coil49 of the relay LR. The operation of the relay BR opens the contactmembers |32 to insert the resistor |45 in the circuit for the spottingcoil and closes contact members |41 to shunt a portion of the resistor|45 from the circuit for the rate coil 52. The energizing circuit forthe rate coil 43 may be traced from positive through either contactsegment |48 and the. resistoridy to a conductorll or through contactsegment '|51 andthe resistor 55 to the conductorl |49, thence throughthe rate coi-l 48 to ground. The energizing circuit .for the actuatingcoil of the relay BR may be traced from positive through a contactsegment |52 of the controller BC, conductor |53, andtheactuating coil ofthe relay BR. to ground.

The operation of the relay BR. also vdeenergizes the switch S, therebyremoving the shunting circuits from the eld windings tor-the motors IUand IE, which increases the excitation of these fmotors and permits themto increase the braking current generated and causes lan increase-inlthe braking effect on the vehicle.

As explained hereinbeore, the accelerator v-is advanced underthejcontrol of the-limit relay `during' dynamic braking, therebycontrolling the braking `current'by varying the resistance in the motorCircuit. The switch M2 is closeuwin, .the event that the accelerator isfully advanced, thereby shunting the resistors v58 Vand 59 `from themotor circuit Vduring dynamic braking in' a kmanner ,similar to thatduring' acceleration of ,the

vehicle;

As previously explained, the closing of the switch M2. at the end of thebraking cycle ,interrupts the energizing circuit for the coil `'Hl ofthe compensating magnet CM by opening aninterlock |51 on the switch M2.The deenergizationof the coil 'it causes the valve to permittheairpressure to build up quickly in the ,brakecyli'riders. In this manner,the braking effect of the air brake is increased as the `dynamic brakeyfades out, thereby maintaining practically the same .rate .ofdeceleration until the vehicle is stopped or the brakes are released.

From the foregoing description, it .isapparent that I have provided vasimplified and improved system for controlling both the accelerationanddeceleration of electrically-propelled'vehicles The present .systemprovides Asmooth operation. of a vehicle Vduring deceleration as well-as during ac celeration of a Vehicle. Furthermore, the present systemmay be readily applied to the control of a plurality of vehiclesoperating in multipleunit trains by duplicating the equipment hereinillustrated and described.

Since many modifications may be made in the apparatus and arrangement ofparts Without departing from the spirit of my invention, I do not wishto be limited other than by the scope of the appended claims.

I claim as my invention:

1. In a control system, in combination, a motor for propelling a vehiclehaving an air-brake system, a power conductor, switching means forconnecting the motorto the power conductor andl for establishing dynamicbraking connections for the motor, a resistor for controlling the motorcurrent during dynamic braking, means for gradually shunting theresistor from the motor` circuit, means responsive to the brakingcurrent for governing the airbrake pressure, and means responsive to theoperation of said first-named resistor shunting means for totallyshunting said resistor and for controlling the operation of saidgoverning means.

2. In a control system, in combination, a motor for propelling a vehiclehaving an air-brake system, a power conductor, switching means forconnecting the motor to the power conductor and for establishing dynamicybraking connections for the motor, a resistor for controlling thelmotor current during" dynamic braking, means for gradually shunting theresistor from the motor circuit, electro-pneumatic means responsive tothe braking current for governing the airbrake pressure, and meansresponsive to the op- `for governing the air-brake pressure, additionalswitching means for shunting the accelerator from the motor circuit, andmeans responsive to the operation of said additional switching means forcontrolling the operation of said electro-pneumatic means.

4. In a control system, in combination, a motor for propelling avvehicle having an air-:brake system, a power conductor, switching meansfor connecting the motor to the power conductor and for establishingdynamic lbraking connections for the motor, a variable resistanceaccelerator for controlling the motor. current during acceleration anddynamic braking of the vehicle, electro-pneumatic means responsive tothe braking current for governing the air-brake pressure, additionalswitching means for shunting the accelerator from the motor circuit, andmeans actuated by the operation of said additional switching means forcontrolling the operation of said electro-pneumatic means.

5. In a control system, in combination, a motor for propelling a vehiclehaving an air-brake system, a power conductor, switching means forconnecting the motor to the power conductor and for establishing dynamicbraking connections for the motor, a variable resistance accelerator forcontrolling the motor current during acceleration and. dynamic brakingof the vehicle, means responsive to the motor current for. controllingthe operation of the accelerator, electro-pneumatic means responsive tothe braking current for gov- .erning the air-brake pressure, additionalswitchingrmeans for shunting the accelerator from the motor circuit, andinterlocking means carried by said additional switching means forcontrolling the operation of said electro-pneumatic means,

6. In a control system, in combination, a motor for propelling a.vehicle having an air-brake system, a power conductor, switching meansfor connecting the motor to the power conductor and for establishingdynamic braking connections for the motor, a variable resistanceaccelerator for controlling the motor current during acceleration anddynamic braking of the vehicle, means responsive to the motor currentfor controlling the operation of the accelerator, electro-pneumaticmeans responsive to the braking current for governing the air-brakepressure, additional switching means for shunting the accelerator fromthe motor circuit upon its operation to a predetermined point, and meansactuated by said additional switching means for controllingtheloperation of said electro-pneumatic means.

7. In a control system, in combination, a motor for propelling a vehiclehaving an air-brake system, a power conductor, switching means forconnecting the motor to the power conductor and for establishing dynamicbraking connections for the motor, a variable resistance accelerator forcontrolling the motor current during acceleration and dynamic braking ofthe vehicle, means responsive to the motor current for controlling theoperation of the accelerator, electro-pneumatic means responsive to thebraking current for governing the air-brake pressure, and additionalswitching means responsive to the operation of the accelerator to apredetermined point for shunting the accelerator from the motor circuitand for controlling the operation of said electro-pneumatic means.

GEORGE R. PURIFOY.

